PHP Manual: Removes duplicate values from an array

Description

array array_unique ( array $array [, int $sort_flags = SORT_STRING ] )

Takes an input array and returns a new array without duplicate values.

Note that keys are preserved. array_unique sorts the values treated as string at first, then will keep the first key encountered for every value, and ignore all following keys. It does not mean that the key of the first related value from the unsorted array will be kept.

Note: Two elements are considered equal if and only if (string) $elem1 === (string) $elem2 i.e. when the string representation is the same, the first element will be used.

Parameters

array

The input array.

sort_flags

The optional second parameter sort_flags may be used to modify the sorting behavior using these values:

Sorting type flags:

SORT_REGULAR - compare items normally (don't change types)
SORT_NUMERIC - compare items numerically
SORT_STRING - compare items as strings
SORT_LOCALE_STRING - compare items as strings, based on the current locale.

Return Values

Returns the filtered array.

Changelog

Version	Description
5.2.10	Changed the default value of `sort_flags` back to `SORT_STRING`.
5.2.9	Added the optional `sort_flags` defaulting to `SORT_REGULAR`. Prior to 5.2.9, this function used to sort the array with `SORT_STRING` internally.

Examples

Example #1 array_unique example


<?php
$input = array("a" => "green", "red", "b" => "green", "blue", "red");
$result = array_unique($input);
print_r($result);
?>

The above example will output:

Array
(
    [a] => green
    [0] => red
    [1] => blue
)

Example #2 array_unique and types


<?php
$input = array(4, "4", "3", 4, 3, "3");
$result = array_unique($input);
var_dump($result);
?>

The above example will output:

array(2) {
  [0] => int(4)
  [2] => string(1) "3"
}

Notes

Note: Note that array_unique is not intended to work on multi dimensional arrays.

array_unique